Rusty; can you quantify this statement: 

 How much more does it cost? 

Over here, it's about $20/gallon plus shipping, which is considerably more than normal antifreeze, and waaaaay more than distilled water.  For cost estimates, you'd be better off to look this up from a local supplier, or contact Evan's about price and shipping down under.    

What percentage poorer, is it in heat removal efficiency

The specific heat of NPG at operating temp (180F) is 0.65;  compared to 0.8 for 50/50 EG/water, and 1.0 for water.  So about 20% poorer than EG/water and 35% poorer than water in carrying heat per unit of volume.

The viscosity of NPG at 180F is about 3.6 times that of EG/water, and about 10 times that of water.  Results in considerably higher pressure drop around the loop and higher pumping power, lower flow rates.  Works best in large channel radiators, and with Evans high performance pumps.

The thermal conductivity is lower (can’t find the data right now).  I’m guessing about 30%.  Results in lower heat transfer cooefficents.

Al